Anxiety disorder is a whole section contained within the DSM5 that comprises of lots of individual sections i.e. Generalised Anxiety Disorder, PTSD etc. This is just meant as a brief outline for anxiety rather than anything more all-encompassing.

All anxiety disorders are based predominately around either anxiety about something that may happen in the future, or fear of either a threat or a danger, be it real or perceived that is immediately about to happen.